Local Environments of Low-redshift Supernovae

We characterize the local (2 kpc sized) environments of Type Ia, II, and Ib/c supernovae (SNe) that have recently occurred in nearby ( d ≲ 50 Mpc) galaxies. Using ultraviolet (UV; from Galaxy Evolution Explorer) and infrared (IR; from Wide-field Infrared Survey Explorer) maps of 359 galaxies and a sample of 472 SNe, we measure the star formation rate surface density (Σ SFR ) and stellar mass surface density (Σ ⋆ ) in a 2 kpc beam centered on each SN site. We show that core-collapse SNe are preferentially located along the resolved galactic star-forming main sequence, whereas Type Ia SNe are extended to lower values of Σ SFR at fixed Σ ⋆ , indicative of locations inside quiescent galaxies or quiescent regions of galaxies. We also test how well the radial distribution of each SN type matches the radial distributions of UV and IR light in each host galaxy. We find that, to first order, the distributions of all types of SNe mirror those of both near-IR light (3.4 and 4.5 μ m, tracing the stellar mass distribution) and mid-IR light (12 and 22 μ m, tracing emission from hot, small grains), and also resemble our best-estimate Σ SFR . All types of SNe appear more radially concentrated than the UV emission of their host galaxies. In more detail, the distributions of Type II SNe show small statistical differences from those of near-IR light. We attribute this overall structural uniformity to the fact that within any individual galaxy, Σ SFR and Σ ⋆ track one another well, with variations in Σ SFR /Σ ⋆ most visible when comparing between galaxies.